INDUCTION HEATING DEVICE AND METHOD OF CONTROLLING INDUCTION HEATING DEVICE

Abstract

 An induction heating device according to an embodiment includes an inverter configured to supply an AC current to a working coil and comprising a plurality of switching elements; a driver configured to supply a switching signal for a switching operation of each switching element to the inverter; and a controller configured to control driving of the working coil by supplying a control signal corresponding to a required power value of the working coil to the driver. In an embodiment, the controller may drive the working coil based on the required power value, measures a resonance current value of the working coil when the working coil is driven, calculate a container efficiency index based on an output current value of the working coil, the required power value, the resonance current value and a limit current value, and control the driving of the working coil based on the container efficiency index.

Description

TECHNICAL FIELD

[0001] The present disclosure relates to an induction heating device and a method for controlling an induction heating device.

BACKGROUND

[0002] An induction heating device generates eddy currents in a metallic container by using a magnetic field that is created around a working coil, to heat the container. As an induction heating device operates, AC currents are supplied to the working coil. As the AC currents are supplied to the working coil, an induced magnetic field is created around the working coil. As the magnetic line of force of the induced magnetic field, created around the working coil, passes through the bottom surface of the metallic container placed on the working coil, eddy currents are generated in the container. As the eddy currents flow in the container, the container is heated by Joule heat that is generated by the resistance of the container.

[0003] Since the container can be heated only when eddy currents are formed in the container by the magnetic field of the working coil, types of containers that can be used in the induction heating device are limited. For example, containers made of materials such as cast iron or casing have high heating efficiency due to their high magnetism. However, containers made of stainless steel have low heating efficiency due to low magnetism.

[0004] When a user uses a container with low heating efficiency, the heating rate of the container may decrease or the temperature of the container may not rise above a predetermined temperature. In this case, since it is difficult for the user to recognize the cause of the heating rate decrease or container temperature decrease, there is a need of providing the user with accurate information about the characteristics and heating efficiency of the container.

[0005] Meanwhile, a user who wants to heat a container using the induction heating device sets a power level corresponding to the thermal power to be supplied to the container. The induction heating device is implemented to drive the working coil based on a required power value corresponding to the power level set by the user.

[0006] Even though the same amount of power is supplied to the working coil driven to heat the container, the size (or magnitude) of the thermal energy supplied to the container could vary based on the characteristics of the container, such as the size, location and material of the container. The energy generated by the working coil but not delivered to the container will circulate in a circuit provided in the induction heating device. The working coil or components disposed around the working coil might have high temperatures or be damaged due to the energy not delivered to the container but circulated in the circuit.

SUMMARY

[0007] One object of the present disclosure is to provide an induction heating device that may provide a user with accurate information about heating efficiency based on characteristics of a container, and a method of controlling the induction heating device.

[0008] Another object of the present disclosure is to provide an induction heating device that may prevent temperature rise or damage of components disposed around a working coil by reducing heat generated inside the induction heating device when a container having low heating efficiency is heated, and a method of controlling the induction heating device.

[0009] One or more of these objects is solved by the features of the independent claims. Aspects according to the present disclosure are not limited to the above ones, and other aspects and advantages that are not mentioned above can be clearly understood from the following description and can be more clearly understood from the embodiments set forth herein.

[0010] An induction heating device according to an aspect may include an inverter configured to supply an AC current to a working coil and comprising a plurality of switching elements; a driver configured to supply a switching signal for a switching operation of each switching element to the inverter; and a controller configured to control driving of the working coil by supplying a control signal corresponding to a (required) power value of the working coil to the driver. The controller may be configured to perform a method according to any one of the aspects and embodiments described herein.

[0011] An induction heating device according to an aspect may include an inverter configured to supply an AC current to a working coil and comprising a plurality of switching elements; a driver configured to supply a switching signal for a switching operation of the switching elements (e.g. to the inverter, in particular to the respective switching elements); and a controller configured to control driving of the working coil by supplying a control signal corresponding to a power value (e.g. a required power value) of the working coil to the driver. The controller may be configured to perform a method according to any one of the aspects and embodiments described herein.

[0012] A method of controlling an induction heating device according to an aspect may include: driving a working coil based on a (required) power value; measuring a resonance current value of the working coil when the working coil is driven; calculating a container efficiency index based on an output current value of the working coil, the (required) power value, the resonance current value and a limit current value; and controlling driving of the working coil based on the container efficiency index. The induction heating device may be an induction heating device according to any one of the aspects and embodiments described herein.

[0013] The induction heating device and/or the method of controlling an induction heating device according to any one of these aspects may include one or more of the following features:

[0014] The (required) power value may be a power value corresponding to a power level set by a user.

[0015] The container efficiency index may be a heating efficiency index of a container to be heated, the heating efficiency index and/or container efficiency index indicating its capability for induction heating. The limit current value may be a preset current value, e.g. a preset maximum current value.

[0016] The induction heating device may further include a rectifier circuit configured to rectify an AC voltage supplied from a power supply device. The induction heating device may further include a smoothing circuit connected to the rectifier circuit and configured to smooth a voltage output from the rectifier circuit. The smoothing circuit may be configured to supply a smoothed voltage to the inverter. That is, the inverter may be connected to the smoothing circuit to receive the smoothed voltage.

[0017] The induction heating device may further include a shunt resistor connected between the smoothing circuit and the inverter. The induction heating device may further include an input current sensor for measuring the current value through, i.e. flowing through, the shunt resistor.

[0018] The induction heating device may further include a voltage sensor to measure a voltage output by the smoothing circuit. In particular, the smoothing circuit may include a DC link capacitor and the voltage sensor may be configured to measure or sense the size of a voltage applied to both ends of the DC link capacitor, i.e. a DC link voltage value.

[0019] The controller may drive the working coil based on the (required) power value, measure a resonance current value of the working coil when the working coil is driven, calculate a container efficiency index based on an output current value of the working coil, the (required) power value, the resonance current value and a limit current value, and control the driving of the working coil based on the container efficiency index. The container efficiency index may refer to a heating efficiency index of a container, e.g. a container to be heated by the working coil.

[0020] The controller may compare the resonance current value to a preset first reference value. When the resonance current value is greater than the first reference value based on the result of the comparison, the controller may calculate the container efficiency index. That is, the controller may only calculate the container efficiency index if the resonance current value is greater than the first reference value.

[0021] The container efficiency index is defined as in [Equation 1] below:

(PEI refers to the container efficiency index and PR refers to the output power value of the working coil WC. PC refers to the (required) power value of the working coil WC and RI refers to the preset limit power value. CI refers to the resonance current value of the working coil WC.)

[0022] The controller may calculate an adjustment value based on the container efficiency index, and adjust the (required) power value by subtracting the adjustment value from the (required) power value.

[0023] The adjustment value may be defined as in [Equation 2] below:

(K refers to the adjustment value and D refers to a preset basic adjustment value. PEI refers to the container efficiency index.)

[0024] The controller may adjust a rotation speed of the cooling fan based on the container efficiency index.

[0025] The rotation speed of the cooling fan may be inversely proportional to the container efficiency index.

[0026] When the container efficiency index is smaller than a preset third reference, the controller may decrease a preset second reference.

[0027] When the resonance current value is greater than the second reference value, the controller may decrease an output power value of the working coil.

[0028] When the (required) power value is determined, the controller may increase the output power value until the output power value of the working coil becomes equal to the (required) power value. When the container efficiency index is smaller than a preset fourth reference value after the output power value becomes equal to the (required) power value, the controller may adjust the output power value to be a value smaller than the (required) power value.

[0029] The container efficiency index is defined as in [Equation 1] below:

(PEI refers to the container efficiency index and PR refers to the output power value of the working coil WC. PC refers to the (required) power value of the working coil WC and RI refers to the preset limit power value. CI refers to the resonance current value of the working coil WC.)

[0030] The container efficiency index may be calculated when the resonance current value is greater than a preset first reference value.

[0031] The controlling the driving of the working coil based on the container efficiency index may comprise calculating an adjustment value based on the container efficiency index and adjusting the (required) power value by subtracting the adjustment value from the (required) power value.

[0032] The adjustment value may be defined as in [Equation 2] below:

(K refers to the adjustment value and D refers to a preset basic adjustment value. PEI refers to the container efficiency index.)

[0033] The method of controlling the induction heating device may further include adjusting a rotation speed of the cooling fan based on the container efficiency index.

[0034] The rotation speed of the cooling fan may be inversely proportional to the container efficiency index.

[0035] The controlling the driving of the working coil based on the container efficiency index may include decreasing a preset second reference when the container efficiency index is smaller than a preset third reference and decreasing an output power value of the working coil when the resonance current value is greater than the second reference value.

[0036] The driving the working coil based on the (required) power value may include increasing the output power value until the output power value until the output power value of the working coil becomes equal to the (required) power value, when the (required) power value is determined.

[0037] The controlling the driving of the working coil based on the container efficiency index may include adjusting the output power value to be a value smaller than the (required) power value, when the container efficiency index is smaller than a preset fourth reference value after the output power value becomes equal to the (required) power value.

[0038] According to the embodiments, the user may be provided with accurate information about heating efficiency based on characteristics of a container.

[0039] In addition, according to the embodiments, the heat generated inside the induction heating device when a container having low heating efficiency is heated may be reduced. Accordingly, the temperature rise or damage of components disposed around a working coil may be prevented.

BRIEF DESCRIPTION OF DRAWINGS

[0040] 

FIG. 1 is an exploded perspective view of an induction heating device according to an embodiment;

FIG. 2 is a circuit block view of an induction heating device according to an embodiment;

FIG. 3 is a flow chart showing a method of controlling an induction heating device according to an embodiment;

FIG. 4 is a flow chart showing a method of controlling an induction heating device according to another embodiment;

FIG. 5 is a flow chart showing a method of controlling an induction heating device according to a further embodiment;

FIG. 6 is a flow chart showing a method of controlling an induction heating device according to a still further embodiment;

FIG. 7 shows an upper plate of an induction heating device according to an embodiment; and

FIG. 8 shows a display provided in an induction heating device according to an embodiment.

DETAILED DESCRIPTION

[0041] The above-described aspects, features and advantages are specifically described hereunder with reference to the accompanying drawings such that one having ordinary skill in the art to which the present disclosure pertains can easily implement the technical idea of the disclosure. In the disclosure, detailed descriptions of known technologies in relation to the disclosure are omitted if they are deemed to make the gist of the disclosure unnecessarily vague. Below, preferred embodiments according to the disclosure are specifically described with reference to the accompanying drawings. In the drawings, identical reference numerals can denote identical or similar components.

[0042] FIG. 1 is an exploded perspective view of an induction heating device according to an embodiment.

[0043] The induction heating apparatus 10 according to an embodiment may include a case 102 defining a body thereof and a cover plate 104 coupled to the case 102 to seal the case 102.

[0044] The cover plate 104 may be coupled to an upper surface of the case to close airtight the space formed inside the case 102 from the outside. The cover plate 104 may include a top plate 106 on which a container for cooking food is placed. The top plate 106 may be made of a tempered glass material such as ceramic glass, but is not limited thereto. The material of the top plate 106 may vary according to embodiments.

[0045] Heating regions 12 and 14 corresponding to working coil assemblies 122 and 124, respectively, may be formed in the top plate 106. Lines or figures corresponding to the heating regions 12 and 14 may be printed or displayed on the top plate 106 in order for a user to clearly recognize the positions of the heating regions 12 and 14.

[0046] The case 102 may have a hexahedral shape with an open top. The working coil assembly 122 and 124 for heating a container or vessel may be disposed in the space formed inside the case 102. In addition, an interface unit 114 may be provided inside the case 102 and have functions to adjust a power level of each heating region 12 and 14 and display related information to the induction heating apparatus 10. The interface unit 114 may be a touch panel that is capable of both inputting information and displaying information by touch, but the interface unit 114 having a different structure may be provided according to embodiments.

[0047] A manipulation region 118 may be formed in a position corresponding to the interface unit 108 in the top plate 106. For user manipulation, characters or images may be printed on the manipulation region 118. The user may perform a desired operation by touching a specific point of the manipulation region 118 with reference to the characters or images pre-printed on the manipulation region 118.

[0048] The user may set the power level of each heating region 12 and 14 through the interface 114. The power level may be indicated by a number (e.g., 1, 2, 3,..., 9) on the manipulation region 118. When the power level for each heating region 12 and 14 is set, the required power value and the heating frequency of the working coil assemblies responding to the respective heating regions 12 and 14 may be determined. A controller may drive each working coil so that the actual output power value can match the required power value set by the user based on the determined heating frequency.

[0049] In the space formed inside the case 102 may be further provided a power source part 112 for supplying power to the working coil assemblies 122 and 124 or the interface unit 114.

[0050] In an embodiment of FIG. 1, two working coil assemblies (i.e., a first working coil assembly 122 and a second working coil assembly 124) are disposed inside the case 102. However, three or more working coil assemblies may be provided in the case 102 according to other embodiments.

[0051] Each working coil assembly 122 and 124 may include a working coil configured to an induced magnetic field using a high frequency alternating current supplied by the power source part 112, and an insulating sheet configured to protect the coil from heat generated by the container. For example, the first working coil 122 shown in FIG. 1 may include a first working coil 132 for heating the container put in the first heating region 12 and a first insulating sheet 130. Although not shown in the drawings, the second working coil 124 may include a second working coil and a second insulating sheet. The insulating sheet may not be provided according to embodiments.

[0052] In addition, a temperature sensor may be provided at the center of each working coil. For example, the temperature sensor 134 may be provided in the center of the first working coil 134 as shown in FIG. 1. The temperature sensor may measure the temperature of the container put in each heating region. In one embodiment of the present disclosure, the temperature sensor may be a thermistor temperature sensor having a variable resistance of which a resistance value changes according to the temperature of the container, but is not limited thereto.

[0053] In the embodiment, the temperature sensor may output a sensing voltage corresponding to the temperature of the container and the sensing voltage output from the temperature sensor may be transmitted to the controller. The controller may check the temperature of the container based on the magnitude of the sensing voltage output from the temperature sensor. When the temperature of the container is a preset reference value or more, the controller may perform an overheat preventing operation of lowering an output power value of the working coil or stopping the driving of the working coil.

[0054] Although not shown in the drawings, a circuit board on which a plurality of circuits or elements including a controller may be disposed in the space formed inside the case 102.

[0055] The controller may perform a heating operation by driving each working coil based on the user's heating start command input through the interface unit 114. When the user inputs a heating terminating command through the interface unit 114, the controller may stop the driving of the working coil to terminate the heating operation.

[0056] A cooling fan 150 may be disposed in a space formed inside the case 102. A third temperature sensor may be disposed inside the case 102. For example, the third temperature sensor may be disposed on a predetermined area of a circuit board provided inside the case 102. The controller may drive the cooling fan 150, when temperature values or temperature change rates that are measured by three temperature sensors are equal to or more than a preset reference value. When the cooling fan 150 is driven, the cold air generated by the cooling fan 150 may be supplied in a direction to a circuit board provided inside the case 102 to cool the working coils 132 and 142 or the components disposed around the working coils 132 and 142. The air after cooling the circuit board may be discharged to the outside of the case 102.

[0057] FIG. 2 is a circuit block view of an induction heating device according to an embodiment.

[0058] The induction heating apparatus 10 according to one embodiment may include a rectifier circuit 202, a smoothing circuit 203, a first inverter (or a first inverter circuit) 212, a working coil WC, a second inverter (or a second inverter circuit) 214, a second working coil 142, a controller 2 and a drive circuit (or driver) 22.

[0059] The rectifier circuit 202 may include a plurality of diodes. According to the embodiment, the rectifier circuit 202 may be a bridge diode circuit and it may be another type circuit according to other embodiments. The rectifier circuit 202 may be configured rectify the AC input voltage supplied from the power source 20, thereby outputting a voltage having a pulsating waveform.

[0060] The smoothing circuit 203 may smooth the voltage rectified by the rectifier circuit 32 and output a DC link voltage. The smoothing circuit 203 may include an inductor L and a DC link capacitor CD.

[0061] The inverter 212 may include a first switching element SW1, a second switching element SW2, a first capacitor C1 and a second capacitor C2. The first switching element SW1 may be connected in series to the second switching element SW2. The first capacitor C1 may be connected in series to the second capacitor C2. The first working coil 132 may be connected between the connection point of the first switching element SW1 and the second switching element SW2 and the connection point of the first capacitor C1 and the second capacitor C2. The inverter 212 may convert the current output from the smoothing circuit 204 into AC current, and may supply the converted AC current to the working coil WC.

[0062] In an embodiment, the first switching element SW1 and the second switching element SW2 may be alternately turned on and off.

[0063] The controller 2 may be configured to output a control signal for controlling the drive circuit 22. The drive circuit 22 may supply switching signals S1 and S2 to the switching elements SW1 and SW2, respectively, based on the control signal supplied by the controller 2. The first switching signal S 1 and the second switching signal S2 may be Pulse Width Modulation (PWM) signals having a predetermined duty cycle.

[0064] When receiving the AC current output from the inverter 212, the working coils WC may be driven. When the working coil WC is driven, eddy currents may flow through the container put on the working coil WC to heat the container. The size (or magnitude) of the thermal energy supplied to the container may vary based on the size of the power substantially generated by the working coil when the working coil WC is driven, that is, actual output power values of the working coil.

[0065] For example, when the user changes an operation state of the induction heating device 10 into a Power On state through the manipulation region 130, power may be supplied to the induction heating device 10 from an external power supply 20 and the induction heating device 10 may enter a driving standby state. Hence, the user may put a container on the first heating region 12 and/or the second heating region 14 provided in the induction heating device 10 and set a power level for the first heating region 12 and/or the second heating region 14 to input a heating-start command. Once the user inputs the heating start command, the controller 2 may determine a required power value of the working coil WC corresponding to the power level set by the user.

[0066] Upon receiving the heating start command, the controller 2 may determine a frequency corresponding to the required power value of the working coil WC, that is, a heating frequency, and may supply a control signal corresponding to the determined heating frequency to the drive circuit 22. Accordingly, switching signals S1 and S2 may be output from the drive circuit 22, and may be input to the switching elements SW1 and SW2, respectively, to drive the working coil WC. When the working coil WC is driven, the container put on the working coil WC may be heated.

[0067] In an embodiment, the induction heating device 10 may include a shunt resistance RS1. The first shunt resistance RS 1 may be connected between the smoothing circuit 203 and the inverter 212.

[0068] In an embodiment, the induction heating device 10 may include an input current sensor 31 configured to sense the size of current flowing through the shunt resistance RS1, that is, a current value. The controller 2 may be configured to sense the size of the current input to the working coil WC based on the current value sensed through the shunt resistor RS1.

[0069] In an embodiment, the controller 2 may sense the size of the voltage applied to both ends of the DC link capacitor CD by using the voltage sensor 35.

[0070] In an embodiment, the controller 2 may determine an output power value of the working coil WC based on [Equation 1].

[0071] In [Equation 1], P refers to an output power value of each working coil 132 and 142. Vdc refers to the size of the voltage applied to both ends of the DC link capacity CD, that is, a DC link voltage value. Iavg refers to an average value of the current value sensed by each shunt resistor RS 1 and RS2.

[0072] The method in which the controller 2 calculates the output power value of the working coil WC based on [Equation 1] is just one of examples. The controller 2 may calculate the output power value of the working coil WC based on other methods well-known in the art.

[0073] In an embodiment, the controller 2 may measure the size of resonance current generated by the working coil WC, that is, a resonance current value of the working coil WC by using a resonance current sensor 35, when the working coil WC is driven. The controller 2 may calculate a container efficiency index based on the resonance current value measured by the resonance current sensor 35. The controller 2 may adjust an output power value of the working coil WC based on the resonance current value measured by the resonance current sensor 35.

[0074] FIG. 3 is a flow chart showing a method of controlling an induction heating device according to an embodiment.

[0075] When the user places a container on the working coil WC and sets a power level, the controller 2 may determine a required power value corresponding to the set power level. The controller 2 may drive the working coil WC based on the determined required power value (302).

[0076] When the working coil WC is driven, the controller 2 may measure a resonance current value of the working coil WC by using the resonance current sensor 35 (304).

[0077] The controller 2 may calculate a container efficiency index based on an output power value, a required power value and a resonance current value of the working coil WC and a preset limit current value (306).

[0078] In an embodiment, the controller may compare the resonance current value to a preset first reference value, and may calculate a container efficiency index when the resonance current value is greater than the first reference value based on the result of comparison.

[0079] In an embodiment, the container efficiency index may be defined as in [Equation 2] below.

[0080] Here, PEI refers to the container efficiency index and PR refers to the output power value of the working coil WC. PC refers to the required power value of the working coil WC and RI refers to the preset limit power value. CI refers to the resonance current value of the working coil WC.

[0081] The resonance current value as well as the output value of the working coil WC is reflected in the container efficiency index defined in [Equation 2]. Accordingly, the user may be provided with accurate information about the heating efficiency of the container placed on the working coil WC.

[0082] In [Equation 2], (PR/PC) refers to the rate of the actual output power value (PR) of the working coil WC to the required power value (PC) of the working coil WC. In other words, the working coil WC is driven based on the required power value PC. Then, the closer the actual output power value PR of the working coil WC is to the required power value PC, the higher the heating efficiency of the container is. In an embodiment, a relational expression of (PR / PC) ≤1 may be established.

[0083] In [Equation 2], (RI/CI) is the rate of the limit current value to the resonance current value of the working coil WC. The limit current value is a preset value and it may be set to be variable according to embodiments. As will be described later, the controller 2 may reduce the output power value of the working coil WC, when the resonance current value is greater than the preset reference value, to prevent the temperature rise of the components around the working coil WC. In other words, if the resonance current value of the working coil WC is high even when the high (PR/PC) value is high, the output power value of the working coil WC may be low. Accordingly, when the (RI/CI) value is reflected in the container efficiency index, the actual output value of the working coil WC based on the output control based on the resonance current value of the working coil WC may be accurately predicted.

[0084] In an embodiment, a relational expression of (PR / CI)≥1 may be established. The greater the resonance current value is, the smaller the (RI/CI) value is. The smaller the resonance current value is, the greater the (RI/CI) value is.

[0085] The controller 2 may control the driving of the working coil WC based on the calculated container efficiency index (308).

[0086] In an embodiment, the operation of controlling the driving of the working coil WC based on the container efficiency index (308) may include calculating an adjustment value based on the container efficiency index and adjusting the required power value by subtracting the adjustment value from the required power value.

[0087] In an embodiment, the adjustment value may be defined as [Equation 3] below.

[0088] Here, K refers to the adjustment value and D refers to a preset basic adjustment value. PEI refers to the container efficiency index.

[0089] In [Equation 3], the preset basic adjustment value D may be set to be variable according to embodiments.

[0090] In an embodiment, the controller 2 may adjust a rotation speed of the cooling fan 150 based on the container efficiency index. In an embodiment, the rotation speed of the cooling fan 150 may be inversely proportional to the container efficiency index.

[0091] The container is heated by the working coil WC. At this time, the lower the container efficiency index is, the greater the resonance current value of the working coil WC is. As the resonance current value becomes greater, the energy generated by the working coil WC is not transferred to the container, only to increase the terminal energy of the working coil WC or components around the working coil WC. Accordingly, the possibility of overheating or damage to the components disposed around the working coil WC could increase. The controller 2 may suppress the temperature rise of the components around the working coil WC by increasing the rotation speed of the cooling fan 150, as the container efficiency index becomes lower.

[0092] When the rotation speed of the cooling fan 150 is controlled based on the container efficiency index, the rotation speed of the cooling fan 150 may be adjusted in advance before the temperature of the components around the working coil WC rises. Due to this structure, it is possible to preemptively suppress the temperature rise of the components around the working coil WC.

[0093] In an embodiment, the operation of controlling the driving of the working coil WC based on the container efficiency index (308) may include reducing a preset second reference value when the container efficiency index is smaller than a preset third reference value; and reducing the output power value of the working coil WC, when the resonance current value is greater than a second reference value.

[0094] As described above, as the resonance current value becomes greater when the working coil WC is driven, the temperature of the components around the working coil WC could rise. Accordingly, the controller 2 may lower the resonance current value of the working coil WC by lowering the output current value of the working coil WC, when the resonance current value is greater than the present second reference value.

[0095] As described above, as the resonance current value of the working coil WC becomes greater, the container efficiency index becomes smaller. When the container efficiency index is smaller than the preset third reference value, the controller 2 may decrease the preset second reference value. The lower the container efficiency index is, the lower the second reference value is. Accordingly, the controller may preemptively suppress the temperature rise of the components around the working coil WC during the driving process of the working coil WC.

[0096] In an embodiment. The operation of driving the working coil WC based on the required power value may include increasing the output power value until the output power value of the working coil is equal to the required power value after the required power value is determined. The operation of controlling the driving of the working coil WC based on the container efficiency index (308) may further include adjusting the output power value to be a smaller value than the required power value, when the output power value of the working coil WC is equal to the required power value.

[0097] As described above, as the container efficiency index is lower and lower (i.e., the resonance current value is higher and higher), the controller 2 may lower the output power value of the working coil WC based on the resonance current value. In this instance, when the output power value of the working coil WC becomes lower, the heating speed of the container heated by the working coil WC could decrease or the temperature of the container could not rise sufficiently. Accordingly, when the container efficiency index is smaller than a preset fourth reference value at the time the output power value of the working coil WC is equal to the required power value, the controller 2 may adjust in advance the output power value to be a value smaller than the required power value, thereby preventing the sudden output deterioration of the working coil WC due to the control based on the resonance current value.

[0098] FIG. 4 is a flow chart showing a method of controlling an induction heating device according to another embodiment.

[0099] The user may place a container on the working coil WC and set a power level through the manipulation region 118 (402).

[0100] When the power level is set, the controller 2 may determine a required power value corresponding to the power level set by the user, and may drive the working coil WC based on the determined required power value (404). For example, the controller 2 may gradually increase the output power value of the working coil WC until the output power value of the working coil WC is equal to the required power value.

[0101] When the working coil WC is driven, the controller 2 may measure a resonance current value of the working coil WC by using the resonance current sensor 35 (406).

[0102] The controller 2 may compare the measured resonance current value to a preset first reference value (408). When the resonance current value is smaller than the first reference value based on the result of the comparison, the controller 2 may constantly drive the working coil WC based on the required power value.

[0103] When the resonance current value is greater than the first reference value based on the result of the comparison (408), the controller 2 may calculate a container efficiency index (410). In an embodiment, the controller 2 may calculate the container efficiency index based on the output power value, the required power value and the resonance current value of the working coil WC and a preset limit current value. For example, the container efficiency index may be defined as in [Equation 2] below.

[0104] After calculating the container efficiency index, the controller may calculate an adjustment value based on the container efficiency index (412). In an embodiment, the controller 2 may calculate the adjustment value based on [Equation 3].

[0105] The controller 2 may adjust the required power value by subtracting the adjustment value from the required power value (414). After adjusting the required power value, the controller 2 may perform the operation (404) again.

[0106] According to the embodiment shown in FIG. 4, when the container having low container efficiency index is heated, the required power value may become smaller. Accordingly, when the container having the low container efficiency index is heated, the possibility of overheating or damage to the components around the working coil WC may be reduced.

[0107] FIG. 5 is a flow chart showing a method of controlling an induction heating device according to a further embodiment.

[0108] The user may place a container on the working coil WC and set a power level through the manipulation region 118 (502).

[0109] When the power level is set, the controller 2 may determine a required power value corresponding to the power level set by the user, and may drive the working coil WC based on the determined required power value (504). For example, the controller 2 may gradually increase the output power value of the working coil WC until the output power value of the working coil WC is equal to the required power value.

[0110] When the working coil WC is driven, the controller 2 may measure a resonance current value of the working coil WC by using the resonance current sensor 35 (506).

[0111] The controller 2 may calculate a container efficiency index (508). In an embodiment, the controller 2 may calculate the container efficiency index based on the output power value, the required power value and the resonance current value of the working coil WC and a preset limit current value. For example, the container efficiency index may be defined as in [Equation 2] below.

[0112] The controller 2 may compare the calculated container efficiency index to a preset third reference value (510). Unless the container efficiency index is smaller than the third reference value based on the result of the comparison, the controller 2 may perform the operation (514). When the container efficiency index is smaller than the third reference value based on the result of the comparison operation (510), the controller 2 may decrease the preset second reference value (512).

[0113] The controller 2 may compare the resonance value to the preset second reference value (514). Unless the resonance current value is greater than the second reference value based on the result of the comparison operation (514), the controller may constantly drive the working coil WC based on the required power value. When the resonance current value is greater than the second reference value based on the result of the comparison, the controller 2 may decrease the output power value of the working coil WC (516).

[0114] According to the embodiment shown in FIG. 5, when the resonance current value of the working coil WC is greater than the second reference value, the output power value of the working coil WC may be decreased. Accordingly, the overheating of the working coil WC or the damage to the components around the working coil WC may be prevented.

[0115] According to the embodiment shown in FIG. 5, when the container efficiency index is smaller than the third reference value, the second reference value may be decreased. When the container having low container efficiency index is heated, the resonance current value of the working coil WC and the temperature of the working coil WC could be suddenly increased. Accordingly, the controller may decrease the second reference value when heating the container having a container efficiency index, thereby preventing the sudden increase of the resonance current value of the working coil WC and the sudden temperature rise of the working coil. Accordingly, the possibility of overheating or damage to the components around the working coil WC may be reduced.

[0116] FIG. 6 is a flow chart showing a method of controlling an induction heating device according to a still further embodiment.

[0117] When a power level is set by the user, the controller 2 may determine a required power value corresponding to the power level set by the user, and may drive the working coil WC based on the required power value. For example, as shown in FIG. 6, the controller 2 may gradually increase the output power value of the working coil WC from 0 (zero) until the output power value of the working coil WC is equal to the required power value.

[0118] If the required power value is P1, the controller 2 may gradually increase the output power value of the working coil WC from 0 to P1. When the output power value of the working coil WC becomes P1 at a time point TA, the controller 2 may calculate the container efficiency index. In an embodiment, the controller may calculate the container efficiency index based on the output power value, the required power value and the resonance current value of the working coil WC and a preset limit current value. For example, the controller 2 may calculate the container efficiency index based on [Equation 2].

[0119] The controller 2 may compare the calculated container efficiency index to a preset third reference value. When the container efficiency index is smaller than a fourth reference value based on the result of the comparison, the controller 2 may gradually decrease the output power value of the working coil WC to a value smaller than the required power value of the working coil WC (e.g., P1).

[0120] As described above referring to FIG. 5, when the container efficiency index is low (i.e., when the resonance current value is higher), the controller 2 may lower the output power value of the working coil WC based on the resonance current value. At t his time, if the output power value of the working coil WC is suddenly lowered, the heating speed of the container heated by the working coil WC could deteriorate or the temperature of the container could not rise sufficiently. Accordingly, like the embodiment of FIG. 6, the controller 2 may adjust in advance the output power value to be a value (e.g., P2) smaller than the required power value, when the container efficiency index is smaller than the present fourth reference value after the output power value of the working coil WC becomes equal to the required power value (e.g., P1). Accordingly, sudden output deterioration of the working coil WC due to the sudden increase of the resonance current value may be prevented.

[0121] FIG. 7 shows an upper plate of an induction heating device according to an embodiment.

[0122] Referring to FIG. 7, three heating regions 12, 14 and 16 may be disposed on the upper plate 106 of the induction heating device according to an embodiment. In addition, a manipulation region 118 may be disposed on the upper plate 106 to control the heating operation for the container disposed on the heating region 12, 14 and 16.

[0123] A button and a display portion may be disposed in the manipulation region 118 to control the heating operation for the container. The user may apply or cut off power to the induction heating device by touching a power button 702. Whether or not power is applied may be displayed by whether or not a power lamp 712 is luminescent.

[0124] In addition, the user may change a current state of the manipulation region 118 to a locked state or an unlocked state by touching a lock button 704 for a preset time period. When the manipulation region 118 is in the locked state, input to all the buttons provided in the manipulation region 118 may be shut off. The locked state of the induction heating device may be displayed by luminescence of the lock button 714.

[0125] The user may set or cancel a container automatic sensing function by touching an automatic sensing button 706. When the container automatic sensing function is set and a container is placed on the heating region 12, 14 and 16, whether or not the container is useable may be displayed on the heating region selecting window 722.

[0126] The user may select the heating region to heat by touching heating region selection buttons 722a, 722b and 722c corresponding to the heating regions 12, 14 and 16, respectively. Then, the user may set an output level for the selected heating region by touching an output level set button 708.

[0127] In addition, the user may set a timer for the selected heating region by touching timer buttons 7. The time set by the user using the timer buttons 710 and 712 may be displayed on a timer window 730.

[0128] The user may check the container efficiency index of the container placed on the heating region in real time by touching a specific button provided in the manipulation region 118.

[0129] For example, while a heating operation is performed after the user may set an output level to 7 in a state of placing the container on the heating region 16 selected by touch the heating region selection button 722a, the user may simultaneously touch a lock button 704 and a heating region selection button 722c to make a command of outputting the container efficiency index of the container placed on the heating region 16.

[0130] Based on the user's command, the controller 2 may calculate the container efficiency and display the calculated container efficiency index on the time window 730 for a preset time period (e.g., 3 seconds). As one example, when the calculated container efficiency index is 0.2, the controller 2 may display the number of '20' or '2' indicating that the current container efficiency index is 20% on the timer window 730.

[0131] FIG. 8 shows a display provided in an induction heating device according to an embodiment.

[0132] As shown in FIG. 8, the induction heating device according to another embodiment may include a display 80 for displaying information related to the operation of the induction heating device, which is separately provided from the manipulation region 118 shown in FIG. 7. The display 80 may be realized by a display device such as LCD but the embodiment is not limited thereto.

[0133] The display 80 may display heating region icons 82, 84, 86 corresponding to the heating regions 12, 14 and 16, respectively. As described above, when the user makes the command of outputting the container efficiency index of the container placed on the heating region by touching the lock button 704 and the heating region selection button 722c at the same time or touching a separate button, the controller 2 may display the container efficiency index (e.g., 40%) of the container placed on the icon 86 corresponding to the heating region 16.

[0134] According to the embodiments, when the user makes the command of outputting the container efficiency index of the container placed on the heating region by using the predetermined button combination or the separate button, the corresponding container efficiency index may be displayed in real time on the manipulation region or the display.

[0135] As described above, the container efficiency index may be variable based on characteristics of the container. However, it is impossible for the user to recognize its characteristics only with the outer appearance of the container or to directly recognize its characteristics in a process of cooking food using the container.

[0136] However, according to the embodiments, the accurate container efficiency index of the container currently heated on the heating region may be displayed in real time based on the user's request. Accordingly, the user can check the characteristics of the container very easily and quickly.

[0137] The embodiments are described above with reference to a number of illustrative embodiments thereof. However, the present disclosure is not intended to limit the embodiments and drawings set forth herein, and numerous other modifications and embodiments can be devised by one skilled in the art. Further, the effects and predictable effects based on the configurations in the disclosure are to be included within the range of the disclosure though not explicitly described in the description of the embodiments.

Claims

1. An induction heating device comprising:

an inverter (212) configured to supply alternating current to a working coil (WC) and comprising a plurality of switching elements (SW1, SW2);

a driver (22) configured to supply a switching signal (S1, S2) for a switching operation of the switching elements (SW1, SW2); and

a controller (2) configured to control driving of the working coil (WC) by supplying a control signal corresponding to a power value of the working coil (WC) to the driver (22),

wherein the controller (2) is configured to drive the working coil (WC) based on the power value, to measure a resonance current value of the working coil (WC) when the working coil (WC) is driven, to calculate a container efficiency index based on an output current value of the working coil (WC), the power value, the resonance current value and a limit current value, and to control the driving of the working coil (WC) based on the container efficiency index.

2. The induction heating device of claim 1, wherein the container efficiency index is defined as in [Equation 1] below:

(PEI refers to the container efficiency index and PR refers to the output power value of the working coil WC. PC refers to the power value of the working coil WC and RI refers to the preset limit power value. CI refers to the resonance current value of the working coil WC.)

3. The induction heating device of claim 1 or 2, wherein the controller (2) is configured to compare the resonance current value to a preset first reference value, and when the resonance current value is greater than the first reference value based on the result of the comparison, the controller (2) is configured to calculate the container efficiency index.

4. The induction heating device according to any one of the preceding claims, wherein the controller (2) is configured to calculate an adjustment value based on the container efficiency index, and to adjust the power value by subtracting the adjustment value

5. The induction heating device of claim 4, wherein the adjustment value is defined as in [Equation 2] below:

(K refers to the adjustment value and D refers to a preset basic adjustment value. PEI refers to the container efficiency index.)

6. The induction heating device according to any one of the preceding claims, further comprising a cooling fan (150) disposed adjacent to the working coil (WC) for cooling the same,
wherein the controller (2) is configured to adjust a rotation speed of the cooling fan (150) based on the container efficiency index.

7. The induction heating device of claim 6, wherein the rotation speed of the cooling fan (150) is controlled to be inversely proportional to the container efficiency index.

8. The induction heating device according to any one of the preceding claims, wherein when the container efficiency index is smaller than a preset third reference value, the controller (2) is configured to decrease a preset second reference value, and
when the resonance current value is greater than the second reference value, the controller (2) is configured to decrease an output power value of the working coil (WC).

9. The induction heating device according to any one of the preceding claims, wherein when the power value is determined, the controller (2) is configured to increase the output power value until the output power value of the working coil (WC) becomes equal to the power value, and
when the container efficiency index is smaller than a preset fourth reference value after the output power value becomes equal to the power value, the controller (2) is configured to adjust the output power value to be a value smaller than the power value.

10. A method of controlling an induction heating device comprising:

driving (302, 404, 504) a working coil (WC) based on a power value;

measuring (304, 406, 506) a resonance current value of the working coil (WC) when the working coil (WC) is driven;

calculating (306, 410, 508) a container efficiency index based on an output current value of the working coil, the power value, the resonance current value and a limit current value; and

controlling (308; 412, 414; 512, 516) driving of the working coil (WC) based on the container efficiency index.

11. The method of controlling the induction heating device of claim 10, wherein the container efficiency index is calculated when the resonance current value is greater than a preset first reference value.

12. The method of controlling the induction heating device of claim 10 or 11, wherein controlling the driving of the working coil (WC) based on the container efficiency index comprises:
calculating (412) an adjustment value based on the container efficiency index and adjusting (414) the power value by subtracting the adjustment value from the power value.

13. The method of controlling the induction heating device of claim 10 or 11, wherein controlling the driving of the working coil (WC) based on the container efficiency index comprises:
decreasing (512) a preset second reference value when the container efficiency index is smaller than a preset third reference value and decreasing (516) an output power value of the working coil (WC) when the resonance current value is greater than the second reference value.

14. The method of controlling the induction heating device of claim 10, 11, 12 or 13, further comprising:
adjusting a rotation speed of a cooling fan (150) for cooling the working coil (WC), based on the container efficiency index, wherein the rotation speed of the cooling fan (150) is controlled to be inversely proportional to the container efficiency index.

15. The method of controlling the induction heating device of claim 10, wherein the driving (302, 404, 504) the working coil (WC) based on the power value comprises:

increasing the output power value until the output power value of the working coil (WC) becomes equal to the power value, when the power value is determined; and/or

wherein controlling the driving of the working coil (WC) based on the container efficiency index comprises:
adjusting the output power value to be a value smaller than the power value, when the container efficiency index is smaller than a preset fourth reference value after the output power value becomes equal to the power value.

Drawing